-LRB- CNN -RRB- -- Troops joined rescue operations in Yunnan province , southwestern China Monday following a 6.1-magnitude earthquake but the search for survivors was hampered by rainfall and aftershocks .

At least 398 people have been killed , and 1,801 injured by the quake that struck on Sunday afternoon , state-run media has reported .

The quake struck at 4.30 p.m. local time -LRB- 4.30 a.m. ET -RRB- . The majority of the casualties occurred in the city of Zhaotong , Ludian County .

The epicenter of the quake was recorded in Longtoushan Township , 23 kilometers -LRB- 14 miles -RRB- southwest of Zhaotong , and tremors were felt almost 200 miles away . Hundreds of aftershocks have been recorded following the initial tremor .

Beijing has allocated 600 million yuan -LRB- $ 97 million -RRB- for relief efforts , Xinhua reported Monday .

It is a fairly remote , partly mountainous area . Many live in low-rise houses made of wood and bricks or plaster , which make them prone to collapse .

Poor housing

The quality of the housing , along with the higher-than-average population density in the area and the relatively shallow epicenter of the quake , was said to be a contributing factor to the death toll .

`` Most rural houses in the county were made of brick or wood , were not designed to be resistant to quakes , and many of them were outdated , '' the China Earthquake Administration said in a statement .

Lu Xuefeng , head of Zhaotong City 's communications department , told reporters Monday that an estimated 210,000 households and almost a million residents had been affected by the earthquake .

He said local authorities had dispatched 6,000 troops to join the disaster relief operation , according to state media . They are joined by specially-trained functionaries , medical teams and thousands of volunteers . Civil authorities have distributed tents , folding beds , blankets and clothing .

`` I was working ... when my family called and told me our home was destroyed , '' Mao Quan , a resident of Longquan village , Longtoushan Township , told CNN .

`` They told me nearly all houses at the village have been destroyed in the earthquake . There 's no shelter , not enough to eat and the roads are cut off so it 's hard for aid to go in . I 've been walking back to the village since 7 a.m. I tried to hitchhike but it 's hard . I 'll probably be back home in another two hours . ''

Some 12,000 homes were destroyed and 30,000 others damaged in Sunday 's quake , according to CCTV . Tens of thousands have been relocated from structurally unsafe houses . Some roads have been destroyed and some villages remain cut off .

Power outages

Ten towns and townships faced power outages overnight . Power was restored to around 19,000 homes Monday morning , but communications remain spotty .

President Xi Jinping called for `` all-out efforts '' in relief operations late Sunday night , with top priority given to saving lives , minimizing casualties and providing adequate shelter for displaced victims of the disaster .

Two commercial planes from carrier China Eastern Airlines have been used to fly rescue and medical teams close to the epicenter .

Premier Li Keqiang , who visited stricken areas on Monday morning , also called for a swift response , urging local authorities to focus attention on search and rescue and also on providing adequate supplies and medical attention for residents affected by the disaster .

Walking for several miles on foot to reach the worst-hit areas , he called on eight government ministries , including civil affairs , health , transport and housing , to send teams to take part in rescue and rehabilitation work .

The scope of the disaster meant that medical facilities were in danger of being overwhelmed .

Officials from Zhaotong urged people to give blood in order to make up a significant shortfall .

Video of the site from CCTV shows rescue workers digging with their hands under several feet of rubble that included dirt , rebar and concrete blocks .

Footage also showed injured adults and children being rushed to hospitals in ambulances .

Power and telephone outages were complicating assessment of the damage , rescuers said . Rain is expected in the next few days , which authorities fear could impact rescue efforts .

Condolences

The White House sent its condolences Sunday , and offered assistance .

`` Our thoughts and prayers are with the families of those that lost their lives , those injured or displaced , and all the people of China on this difficult day , '' National Security Council Deputy Spokesperson Bernadette Meehan said in a statement .

`` U.S. disaster response officials are in contact with their Chinese counterparts . The United States stands ready to assist . ''

The United Nations echoed the sentiment .

'' -LRB- The Secretary General -RRB- offers his condolences to the Chinese Government and the families of those killed , and his deepest sympathies to those who were injured or otherwise affected in this disaster , '' Secretary General Ban Kee Moon 's spokesperson said in a statement , adding that the organization was ready to `` respond to humanitarian needs '' and to `` mobilize international support '' as needed .

The U.S. Geological Survey said the quake had a magnitude of 6.1 , while the China Earthquake Networks Center reported it as a 6.5-magnitude event .

The area is a mountainous region , known for its natural scenery and ethnic diversity , but is also prone to natural disasters and lies on a major earthquake fault .

Yunnan 's neighboring province , Sichuan , witnessed a magnitude 7.9 earthquake in 2008 where at least 87,000 people died .

Measuring the magnitude of earthquakes

What to know about earthquakes

CNN 's Jaime FlorCruz and Dayu Zhang in Beijing contributed to this report .

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At least 398 dead in quake , Chinese state-run TV says ; 1,801 people injured

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Tens of thousands of homes damaged or destroyed

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China Earthquake Networks Center says the magnitude was 6.5